A typical liquid crystal display generally includes a display panel and a backlight module for illuminating the display panel. The display panel includes two glass substrates, and a liquid crystal layer is sealed between the substrates. The display panel receives image signals from a data circuit, and displays desired images according to the image signals.
Referring to FIG. 5, this is a block diagram of a conventional liquid crystal display 100, showing an image displaying process thereof. The liquid crystal display 100 includes a timing control and video output unit 110, a scanning circuit 120, a data circuit 130, and a liquid crystal panel 140 having a plurality of pixels (not shown) defined thereon. The timing control and video output unit 110 includes a converter circuit 111.
Image signals YCbCr are used in the liquid crystal display 100. In general, the image signals YCbCr are compressed, in order to reduce the volume thereof during transmission. The compressed image signals YCbCr are transmitted to the timing control and video output unit 110. Each image signal YCbCr is composed of three factors, a brightness factor Y, and two color factors Cb, Cr. The image signal YCbCr is transformed into a corresponding RGB (red, green, and blue) signal by the converter circuit 111, and is then sent to the data circuit 130. The timing control and video output unit 110 also sends a control signal to the scanning circuit 120. After the RGB signal is processed by the data circuit 130 and the control signal is processed by the scanning circuit 120, the RGB and control signals are sent to the liquid crystal panel 140. An image is displayed through each pixel on the liquid crystal panel 240 according to the control signal and the RGB signal received.
The human eye is more sensitive to brightness diversity than color diversity. Accordingly, each image signal YCbCr received by the timing control and video output unit 110 already has compressed color factors Cb, Cr. Thereby, the volume of the transmitted image signal YCbCr is reduced.
Referring to FIG. 6, this is an abbreviated diagram showing image signals YCbCr divided among the pixels of the liquid crystal panel 140, the image signals YCbCr having a compression pattern of 4:1:1. Generally, while an image is displayed on the liquid crystal panel 240, a color difference occurred among adjacent pixels is slight, whereas a large color difference occurs at adjacent pixels showing an edge of the image. Therefore, a color segment having pixels with a slight or no color difference can be defined. Each image signal YCbCr within each color segment for displaying an image has the same color factors Cb, Cr but different brightness factors Y. For example, for a topmost, leftmost one of the color segments illustrated, the color segment has the same color factors Cb1,1, Cr1,1, but different brightness factors Y1,1, Y1,2, Y1,3, Y1,4 respectively.
During compression of the image signals YCbCr, four adjacent image signals YCbCr arranged in a line are designated to each color segment. The color factors Cb, Cr of the four image signals YCbCr and the brightness factors Y thereof are selected respectively for compression. Then the compressed images signals YCbCr are transmitted.
Referring to FIG. 7, this is an abbreviated diagram showing image signals YCbCr divided among the pixels of the liquid crystal panel 140, the image signals YCbCr having a compression pattern of 4:2:2. The image signals YCbCr within each color segment for displaying an image have the same color factors Cb, Cr but different brightness factors Y. For example, for a topmost, leftmost one of the color segments illustrated, the image signals YCbCr have the same color factors Cb1,1, Cr1,1, but different brightness factors Y1,1, Y1,2 respectively.
During compression of the image signals YCbCr, two adjacent image signals YCbCr arranged in a line are designated to each color segment. The color factors Cb, Cr of the two image signals YCbCr and the brightness factors Y thereof are selected respectively for compression. Then the compressed images signals YCbCr are transmitted.
A benefit of the above-mentioned compressing the image signal YCbCr is to reduce the image signal volume during the transmitting. However, some adjacent image signal showing an edge of an image may have a large color difference therebetween, and a distortion after the image signal YCbCr be transferred into a RGB signal, and a blur may occur in the edge of the displaying image.
Accordingly, what is needed is a liquid crystal display configured to overcome the above-described problems.